The airline industry has seen multiple mergers or acquisitions in the past 10 years: Delta merged with Northwest, American merged with U.S. Airways and United merged with Continental. But one high-profile airline partnership is being torn asunder, as Delta Air Lines and Alaska Airlines announced Monday they would officially terminate their relationship come April 2017.

The airlines, which both serve the Boise Airport, said they would no longer honor each other's frequent flier miles beginning spring 2017. In the meantime, mileage plan members will still be able to earn Delta miles from flights booked on Alaska—and vice versa—but for those who want to use those miles to book travel, they'll need to make reservations and use their miles prior to April 30, 2017.

"The companies also will no longer offer bookings for travel on each other's flights, through the practice known as code sharing," Delta and Alaska officials stated in a joint-statement Monday morning. "Both airlines will retain interline agreements so that they can assist passengers traveling on itineraries requiring multiple airlines."

Industry analysts said the relationship between Alaska and Delta had been deteriorating for some time over competition for some core markets like Las Vegas, Los Angeles and San Francisco, and the Northwest News Network went so far as to label the carriers "frenemies" back in 2013.